David Astro Penta Prism Diagonal - 1.25"

The David Astro Penta Prism 90-Degree Diagonal is a non inverting non reversing diagonal. It’s particularly suited for use with the David Astro Premium Linear BinoViewer, where its unique optical design delivers an accurate image orientation, eliminating the need for image inversion or mental adjustments common with traditional star diagonals.

At the heart of this diagonal is a pentagonal-shaped BK-7 glass prism, multi-coated on its transmitting surfaces and dielectric-coated on the reflective surfaces, which maximizes light transmission to the eyepiece. Unlike standard star diagonals that produce a mirror-reversed image, the Pentaprism Diagonal preserves the natural left-to-right orientation, making it invaluable for star navigation and terrestrial applications.

This 1.25” diagonal features a non-marring compression ring collar and a tapered barrel for secure attachment to any telescope focuser, and it’s threaded for 1.25” filters. With a generous clear aperture of 29mm, the diagonal avoids vignetting even with long focal length and wide-angle eyepieces, preserving field brightness and edge-to-edge clarity.

Designed with an optical path length (backfocus requirement) of 120mm, our Pentaprism Diagonal ensures compatibility with most telescope setups. When paired with the David Astro Premium Linear BinoViewer, it provides a correctly oriented view, ideal for terrestrial observation where orientation accuracy is essential. However, it may not yield the same results with other binoviewers that lack an integrated image-erecting lens.

Enhance your observing experience with the David Astro Pentaprism Diagonal, the ideal choice for astronomers and terrestrial viewers seeking clarity and orientation without sacrificing image quality.